The invention relates to a pump assembly with a housing formed of at least two metallic housing parts, and with at least one diffuser arranged in the housing. Such designs are particularly known with multi-stage pumps, whose housing is formed of several housing parts, which are in each case assigned to a pump stage. Each pump stage comprises a diffuser, which leads the flow exiting from the impeller to a subsequent impeller. These diffusers must be fixed in the inside of the housing. For this, in the case that the diffusers are designed of metal, it is known to weld these in the housing. Moreover, it is known to provide diffusers of plastic with radially projecting projections or with an annular radial projection, which are clamped between the adjacent housing parts. For this, in the state of the art, enlarged bearing surfaces which come into contact with the projections of the diffuser, are provided at the axial ends of the housing parts.
The design of the bearing surfaces on the housing parts however demands an increased manufacturing expense on manufacture of the housing parts.